Our navels, also know as belly buttons, are scars left over from our umbilical cords. While in the mother's womb, a baby receives food and oxygen and rids itself of waste through the umbilical cord. One end of the umbilical cord is attached to the mother's placenta, an organ that develops during a mother's pregnancy for this very special job. The other end is attached to the baby's stomach. As soon as the baby is born and begins breathing on its own, the umbilical cord is cut. After a few weeks, the remains of the cord wither away. All that remains is the navel.

But does your dog have a belly button? Or a better question is, have you ever seen it if it does? Most people haven't. But this doesn't mean that it doesn't exist. Since mammals give birth to live young, they share in common the process of developing inside their mother. This, by necessity, requires a connection between the mother and the baby for the passing of nourishment, oxygen and clearing away waste. Dogs and cats are no different. Although each is born in a fluid-filled sac, it is still connected to its mother's placenta by an umbilical cord. In fact, a mother dog will bite and break each puppy's umbilical cord right after birth. Soon, just like us, all that's left is a scar.

Puppies don't have obvious belly buttons for a few reasons. The size of their umbilical cord is small. Sustaining a human baby requires a bigger umbilical cord, hence a bigger scar. A puppy's scar heals into a small slit rather than a round hole. And the area is quickly covered with fur, making detection more difficult. So next time your dog is taking a snooze on her back, take a look. With some investigation, you'll find its belly button.

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About the Author

Gene Mascoli, JDGene Mascoli is a founder and publisher of ScienceIQ.com. He holds a J.D. degree from the University of Santa Clara and a B.A. in English. In 1997 Gene launched ScienceMaster.com, an online science education portal where he brought together his love of writing with his interest in the sciences. Gene collaborated with David Gamon on the popular digital book
“The Internet Guide to NASA on the Net” and has also produced two popular science CD-ROMs on astronomy and space science.ScienceMaster.com